1. Field of the Invention
The present invention relates to compositions suitable for formation into mild personal cleansing and/or laundry detergent bars. More specifically, it relates to liquid, paste, and flaked compositions suitable for processing into solid or semi-solid suitable for formation into mild personal cleansing and/or laundry detergent bars. Additionally, the compositions are suitable for use in formulated laundry and dish cleaning pastes or gels.
2. Description of the Related Art
Mild personal cleansing and laundry cleaning bar preparations have become a focus of great interest. People wash and exfoliate their skin with various surface-active detergent bar formulations several times a day. Ideal skin cleanser bars should cleanse the skin gently, causing little or no irritation, without defatting and over-drying the skin or leaving it taut after frequent routine use. Most lathering soap bars fail in this respect.
The processability of such bars and their precursor detergent compositions has also become a focus of great interest. The mildness, processability, firmness and smear properties of such bars have become a focus of even greater interest.
Synthetic detergent bars, frequently called "combo bars" (e.g., having substantial amounts of soap) and/or "syndet bars" (e.g., having very little or no soap) are well known to the art, along with natural "soap" bars for personal care use. Syndet bars often possess poor physical properties, e.g., off odors, poor processability, stickiness, brittleness, bar messiness, lather quality, lack of mildness or combinations thereof. Additionally, the problems of formulating synthetic detergent bars are not limited to the performance characteristics of the finished bars. Most bars which are made with certain mild surfactants are very difficult to fabricate.
In contrast, the fabrication of relatively pure "soap" bars is a well-worked-out engineering procedure involving milling, plodding and molding. For example, coco/tallow soap becomes quite plastic when warmed and can be easily plodded and molded under relatively low pressures. However, most synthetic detergents and detergent-filler compositions for use in cleansing or laundry detergent bars do not become plastic and the machinery for fabrication must be specially designed. See U.S. Pat. No. 2,678,921, J. A. V. Turck, Jr., issued May 18, 1954.
Ideal processing of syndet bars or synthetic detergent bars should be fast and problem free in terms of milling, plodding and molding toilet bar formations. Most mild syndet bar processings fall short in some or all of these respects.
Synthetic detergent bar formulations for personal care use are well known to the art. For example, see U.S. Pat. No. 5,328,632, Redd, et al., issued Jul. 12, 1994; U.S. Pat. No. 5,510,050, Dunbar, et al., issued Apr. 23, 1996; U.S. Pat. No. 5,393,449, Jordan, et al., issued Feb. 28, 1995; WO 95/27036, Fakoukakis, et al., filed Mar. 30, 1995; and WO 95/27038, Faoukakis, et al., filed Mar. 30, 1995.
Major drawbacks of most synthetic surfactant toilet bar formulations are harshness, poor lather, poor smear, and poor processability due to stickiness. The use of high sudsing anionic surfactants can yield acceptable lather volume. Unfortunately, the highest sudsing anionic surfactants are, in fact, poor in processability. While some prior art mild blends of sodium coconut/tallow alkyl glyceryl ether sulfonate (AGS) are relatively good in lather potential, they are difficult to process because of their stickiness or hygroscopicity. It will be appreciated that processability, firmness, smear, mildness, lather, and rinsability make surfactant selection and stoicheometry for mild personal cleansing bars a critical and difficult task. Thus, it will be appreciated that rather stringent requirements for formulating mild personal cleansing bars limit the choice of surfactants, and final formulations represent some degree of compromise. Mildness is often obtained at the expense of processability, effective cleansing, lathering, or rinsing, or vice versa. Processability is often obtained at the expense of smear.
Synthetic detergent bar formulations for laundry cleaning are also well known to the art. For example, see WO 95/27036, Fakoukakis, et al., filed Mar. 30, 1995; and WO 95/27038, Faoukakis, et al., filed Mar. 30, 1995. Such laundry detergent bars have found expanded use in regions of the world where automatic clothes washing machines are not common. The ideal laundry detergent bar is effective in cleaning clothes, has acceptable sudsing characteristics, has low smear, and pleasing odor and appearance. As these laundry detergent bars are in contact with the skin during clothes washing, mildness is also highly desirable.
Methods for making laundry detergent bars are well known in the art. For example, see Philippine Pat. No. 23,689, issued Sep. 27, 1989 to Unilever; and Philippine Pat. No. 24,551, issued Aug. 3, 1990 to Unilever. Much like the syndet bars for personal care use, laundry detergent bars often possess the same physical problems, e.g., harshness, poor lather, poor smear, and poor processability due to stickiness.
Thus, a need exists for superior processable, mild personal cleansing and/or laundry detergent bar formulations with good mildness, processability, smear, lather potential and rinsability.
Accordingly, a key aspect of the present invention is the surprising synergy present between an alpha sulfonated alkyl ester and an sulfonated fatty acid. The properties of mono and di salt forms of sulfonated fatty acids (i.e. an alpha sulfonated alkyl ester and a sulfonated fatty acid) have been studied and reported by Stirton (see Stirton, A. J. JAOCS 39, 490-496 "Alpha Sulfo Fatty Acids and Derivatives: Synthesis, Properties and Use"), wherein sulfonated fatty acid disalts (pelargonate, laurate, and myristate) are primarily simple electrolytes, do not have markedly lower surface tension, and do not have significant wetting, foaming, or detergent properties. It is additionally well recognized by those skilled in the art, that sulfonated fatty acids impart improved smear properties, but are very difficult to process into cleansing bars. Also recognized is the fact that alpha sulfonated alkyl esters are too soft and too soluble to produce an acceptable bar alone.
Based on this surprising and unique synergism of alpha sulfonated alkyl esters and sulfonated fatty acids, compositions of the present invention are useful in the production of detergent bars which exhibit improved processability, increased surface tension reduction properties, increased foaming properties, improved color stability, and impart superior feel and after-feel properties to skin.